68Ga-PSMA-11 PET/CT in primary staging of prostate carcinoma: preliminary results on differences between black and white South-Africans

Abstract

Purpose: The incidence of prostate cancer is 60% higher and the mortality rate is two- to three-times greater in black versus white men. We report on differences in ⁶⁸Ga-PSMA-11 PET/CT imaging findings in 77 black South-African (BSAs) and 18 white South-African (WSAs) treatment-naïve primary prostate carcinoma (PPC) patients.

Methods: ⁶⁸Ga-PSMA-11 PET/CT imaging findings were compared to histological, biochemical and morphological imaging data. Patients were grouped into three Gleason grade groups (GG), GG 1 (scores 3 + 3 and 3 + 4), GG2 (scores 4 + 3 and 4 + 4) and GG3 (scores 9 and 10), and the PSA difference among the groups was determined. Inter-racial difference in SUVmax of the primary tumor as well as its correlation with serum PSA were also determined.

Results: Ninety-three out of 95 PPC where readily identified on ⁶⁸Ga-PSMA-11 PET/CT imaging. Median PPC SUVmax and serum PSA values proved significantly higher (p = 0.033 and p = 0.003) in GG3 patients (median 16.4 and 180 ng/ml) when compared to GG1 patients (median 9.6 and 25.1 ng/ml) or GG2 patients (median 8.8 and 46.2 ng/ml). SUVmax significantly correlated with serum PSA-values (r = 0.377 (p = 0.0001)). Age, frequency of lymph node involvement and distant metastases, and GGs (p ≥ 0.153) were similar in BSAs and WSAs, both median serum PSA-values as well as SUVmax values proved significantly higher in BSAs when compared to WSAs, respectively, 81.6 ng/ml versus 14.5 ng/ml (p = 0.0001) and 11.9 versus 4.38 (p = 0.004). Moreover, Gleason-score normalized median SUVmax values proved 2.5 times higher in BSAs when compared to WSAs (p = 0.005).

Conclusion: SUVmax values proved significantly related to GG and to be significantly higher in BSAs when compared to WSAs. Also, SUVmax significantly correlated with serum PSA values, which was significantly higher in BSAs when compared with WSAs.

Keywords: 68Ga-PSMA; Prostate carcinoma; Racial differences.

Fig. 1

Comparison of SUV max values of primary prostate carcinoma for the different Gleason groups according to race (Blue color corresponds to the results obtained in white men, the green color to results obtained in black men)

Fig. 2

Comparison of PSA values for the different Gleason groups (1 to 3) of the entire cohort

Fig. 3

Scatterplot showing the relationship between PSA values and primary tumor related ⁶⁸Ga-PSMA-11 uptake expressed as SUVmax in patients with localized (that is excluding lymph node involvement and/or distant metastases) prostate carcinoma (r = 0.548 (p = 0.0001))

Fig. 4

Comparison between the ratio of SUV max values of primary prostate carcinoma to the Gleason score (ratio) versus the race of the patients (1 corresponds to the results obtained in white South-Africans, 2 corresponds to the results obtained in black South-Africans)

Fig. 5

Comparison of SUV max values of primary prostate carcinoma for two patients with the same Gleason scores (4 + 5) but different races (A) corresponds to a 70-year-old white man, maximum-intensity-projection PET, axial, coronal and sagittal fused PET/CT demonstrated SUVmax of 6.3 in the primary prostate cancer with a PSA of 10.5 ng/mL. (B) corresponds to a 69-year-old black man, maximum-intensity-projection PET, axial, coronal and sagittal fused PET/CT demonstrated SUVmax of 29.2 in the primary prostate cancer with a PSA of 38.71 ng/mL